Good traction and resistance to abrasion are primary considerations for tire treads; however, motor vehicle fuel efficiency concerns argue for a minimization in rolling resistance, which correlates with a reduction in hysteresis and heat build-up during operation of the tire. These considerations are, to a great extent, competing and somewhat contradictory: treads made from compositions designed to provide good road traction usually exhibit increased rolling resistance and vice versa. Efforts to reduce hysteresis should not compromise traction properties, particularly traction performance in wet conditions, a property that combines many complex factors such as tread rubber deformation induced by road surface asperities, rate of water drainage, possible adhesive interactions at the interface between rubber and road surface, and possible interactions between filler particles and road surface components.
Tread compositions typically contain one or more elastomers and one or more types of reinforcing materials such as particulate carbon black and silica; see, e.g., The Vanderbilt Rubber Handbook, 13th ed. (1990), pp. 603-04. Filler(s), polymer(s), and additives typically are chosen so as to provide an acceptable compromise or balance of the desired properties. Ensuring that reinforcing filler(s) are well dispersed throughout the elastomeric material(s) both enhances processability and acts to improve physical properties. Dispersion of filler particles can be improved by increasing their interaction with the elastomer(s) and/or decreasing their interaction with each other.
One method for increasing particle dispersion is through chemical modification of one or more of the elastomers, typically at a terminus by reaction of a living (i.e., anionically initiated) polymer with a functional terminating agent; see, e.g., U.S. Pat. Nos. 3,109,871, 4,647,625, 4,677,153, 5,109,907, and 6,977,281, as well as references cited therein and later publications citing these patents.
A recent approach has involved functionalization with a compound that includes an aryl group that includes multiple hydroxyl functionalities, which has the advantage of being effective with conventional filler particles, such as silica and carbon black, as well as non-conventional mineral particles such as various metal oxides and hydroxides; see WO 09/086490 (int'l appl. no. PCT/US2008/088384). This approach also has shown evidence of providing vulcanizates that exhibit good traction properties, even in wet conditions.
The functionalized polymers described in WO 09/086490 are said to be capable of preparation via solution techniques, with anionic initiation and coordination catalysis as possible propagation techniques. However, certain types of monomers can be difficult or impossible to polymerize by those propagation mechanisms. Accordingly, alternative processes for preparing polymers that include mer resulting from incorporation of compounds that include an aryl group with multiple hydroxyl moieties remain desirable.